Chronic kidney disease is the gradual loss of kidney function over months to years. By the time obvious signs appear, around 65–75% of kidney function is already lost — which is why screening blood and urine tests from age 5–7 catch it years earlier than waiting for symptoms.

Signs include increased thirst and urination (the kidneys can't concentrate urine), weight loss, decreased appetite, intermittent vomiting, bad breath, weakness. Late signs include severe lethargy, mouth ulcers, and pale gums.

Treatment depends on staging (IRIS stages 1–4). Early stages: renal prescription diet, hydration support, blood pressure monitoring. Later stages add phosphorus binders, anti-nausea medication, appetite stimulants, B-vitamin injections, sometimes subcutaneous fluid therapy at home.

The single highest-impact intervention is the renal diet — modified protein, restricted phosphorus, supplemented omega-3. It is unpalatable to many cats; gradual transition over weeks and management of nausea matters.

Caught at IRIS stage 1–2, many cats live years of good quality. Caught at stage 3–4, the timeline is months to a year or two.